What does the last modifier digit mean in russian germanium transistors? P13V(P)

[ELS122]

I know the first letter after the number is the variant, usually differing in gain. But I've found a few that have an additional letter after that P13VP. Is it like for low noise variants similar to tubes?

[Vovk_Z]

Two additional letters together 'ВП' in these ancient transistors mean 'military-grade' ('ВП' = 'военная приемка'). It doesn't mean they are 100% really good but there is a good probability that they are better than those without 'ВП'. They were tested at the factory and good ones have 'ВП' marking and are supposed to military customers.
There are other codes for military grades (e.g. a rhomb) and several military grades inside military grades (1-9). Grade '9' is a good one that meets all requirements and other 1-8 grades are not good (almost a usual junk).
If you have only one letter (А/Б/В/Г) - then it is as you know a usual separation into subtypes under one type (variants, like different hfe or different max voltages, etc.).

Upd.:
Newer design transistors were marked with another marking standard as 'КТ', 'ГТ', '2Т', '1Т', where 'T' is транзистор/transistor.
'1Т' is a military-grade version of 'ГТ' (германий or germanium).
'2Т' is a military-grade version of 'КТ' (кремний or silicon/silicium).